GB2034276A

GB2034276A - Gripping devices

Info

Publication number: GB2034276A
Application number: GB7935758A
Authority: GB
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1978-10-16
Filing date: 1979-10-15
Publication date: 1980-06-04
Also published as: DE2845056A1; IT1118129B; DE2845056C2; IT7949821A0; US4253694A; GB2034276B; FR2439060A1; FR2439060B1

Description

1 GB 2 034 276 A 1

SPECIFICATION Gripping Devices

1 The invention relates to gripping devices for rotationally symmetrical components.

It is known to pick up and to transport rotationally symmetrical components with the help of mechanical gripping devices. Such devices are relatively expensive, and particularly so when a uniform applied force is to be exerted on the entire surface of the object being picked up. The gripping force achieved is exclusively dependent on the frictional engagement of the surfaces which are in contact. In order to obtain satisfactory conditions in this respect, it is therefore usual to provide the gripping fingers of 80 such gripping devices with a surface covering of rubber or other elastomeric materials.

In each case gripping devices of this kind are relatively sensitive to wear and relatively unrobust 20. with respect to unskilled treatment. Repairs are in 85 general expensive and can only be carried out by skilled workers.

The object underlying the invention is to develop a gripping device for rotationally symmetrical components which makes possible 90 the attainment of a high and entirely balanced gripping force, and which has a robust construction and can be restored to good condition by labourers after wear has occurred.

This object is solved according to the invention 95 by gripping devices for rotationally symmetrical components, consisting of a supporting part with at least one circumferential groove having a connection for a liquid or gaseous working medium, and a movable gripping ring arranged in 100 the groove, of an elastomeric material, with on each end surface at least one sealing lip, which engages slidingly against the respective end wall of the groove.

There is a free choice of working medium for 105 operation of a gripping device according to the invention, and both liquid and also gaseous working media can be used. In general a working pressure of 6 kp/cM2 is sufficient. The operating pressure available in compressed air systems as 110 usually installed in factories is thus in general fully sufficient.

A relatively large hydraulically or pneumatically effective surface of the gripping ring can make possible the employment of elastomeric materials with relatively high rigidity. The gripping device can therefore be used with advantage even in relatively rough conditions of operation.

According to one particular construction the groove is in the outer periphery of a supporting part of peg-like shape. This construction provides an internal gripper which, by the compact construction of the supporting part, is able to accept very great radial impact or jolting loads.

The supporting part need not necessarily be brought as a finished component, but by reason of its relatively simple shape it can easily be made with the machine tools which are usual and available in all factories, or altered to suit special circumstances. For the attainment of satisfactory gripping force it is simply necessary to match the constructional tolerances belonging to the previously-made gripping rings, as well as a predetermined surfaced quality. This possibility assists flexibility in the tool store in relation to changing manufacturing programmes.

The same advantages appear with reference to another advantageous construction, in which the groove is in the inner periphery of the bore of a supporting part of sleeve-like shape. This construction provides an external gripper, and, by variation of the working presure, and of the cross section of the gripping ring, or the choice of the elastomeric material employed for its manufacture, one can very exactly determine the gripping force within a wide range. A gripping device of this kind is for example suitable for the lifting and transport of thin-walled crystal glasses, and for the transport of heavy metal pins. A high adaptability to surface irregularities, as occur for example with mouth-blown crystal glasses or with control pistons of valves, can be achieved without more ado.

If there is a plurality of grooves and gripping rings, then preferably the connection for the working medium connects together all the grooves. By this means a fully synchronous and balanced gripping force is achieved by all gripping rings.

Preferably the cross section of the gripping ring is similar to the cross section of the respective groove, and the sealing lips are arranged as projecting annular beads in the neighbourhood of the corners between the respective end surfaces and the outer or inner periphery of the gripping ring. The cross section of the sealing lips can resemble the cross sections of known piston seals. Preferably, when the gripping ring is unstressed, the axial length of its body is a little less than the corresponding dimension of the groove, while the axial distance between edges of the sealing lips is somewhat greater than the dimension of the groove. From the special position of the sealing lips there results a pressing against the end surfaces to be sealed which is only partly dependent on the pressure. From this there results a particularly great elastic flexibility of the gripping rings without influence on the sealing effect.

The grooves have in general a U-shaped cross section, and it has appeared as advantageous that the axial length of the body of the gripping ring inserted in a groove is from 0.8 to 3 times the radial thickness of the body. Here the dimensions relate to the basic cross section of the gripping ring, similar to the cross section of the groove, without regard to the annular beads which project and are provided with the sealing lips. From the maintenance of the above-mentioned ratio there results a particularly great adaptability of the gripping ring together with a particularly high robustness for average operating conditions.

The accompanying drawings show three gripping devices embodying the invention by way 2 GB 2 034 276 A of example. In these drawings:

Figure 1 is an axial section of a first device; Figure 2 is an axial section of a second device; 65 and Figure 3 is a half axial section of a third device, about to grip a bottle neck.

Figure 1 shows an internal gripper comprising a supporting part 1 with a connection 2 for the working medium. The connection 2 is connected via passages with two annular external circumferential grooves 5, in which are arranged movable gripping rings 3 of elastomeric material.

In the neighbourhood of the transitions between the inner periphery of the gripping ring and its end surfaces there is arranged in each case an annular bead 4, one edge of which serves as a sealing lip which engages against the respective end face 6 of the groove. Between the two annular beads there is enclosed a U-shaped space, and for effecting the gripping operation the internal pressure in this inner space is raised by raising the pressure of the working medium through the connection 2.

From this there results an elastic deformation of the gripping ring in the form of an increase in diameter. This is employed for mechanical and frictional holding of the component to be picked up.

Figure 2 shows an external gripper which 90 operates in a generally similar manner. The supporting member 1 is here formed with a sleeve-like shape, and has in the interior a bore 7.

The bore is enlarged in one place in the form of a groove 5, in which is a movable rectangular gripping ring 3. The working medium is supplied through a connection 2, and from an increase of pressure of working medium there results an elastic reduction in diameter of the gripping ring 3. The arrangement and formation of the sealing lips corresponds to the explanation given with reference to Figure 1, In both constructions the gripping rings 3 are simply inserted loosely in the groove or grooves 5 present in the supporting part. With occurrence of 105 wear, it is therefore possible to remove the gripping rings from the grooves by simple elastic enlargement and to replace them by new gripping rings, which can be snapped elastically into the groove.

Figure 3 shows a modification of Figure 2, in which at least one of the corners between the respective end surfaces and the inner periphery of the gripping ring 3 is bevelled at an angle at 8, these being the corners on the side away from the sealing lips 4. Preferably the bevel includes an angle of 45 to 800 with the axis of rotation of the gripping device, and the bevel amounts at a maximum to 50% of the radial extent of the end face of the body of the ring 3. The bevel has principally the object, in conjunction with a step present on the component being gripped, to exert on the latter an additional axial force.

2 Figure 3 shows the neck 10 of a bottle, having an annular circumferential external bead below a scew thread. When the diameter of the gripping ring 3 is reduced by admission of working medium at 2, the bevel 8 engages the bead 9 and exerts an axial upward secondary force. This urges the mouth of the neck against a surface 11 at the top of the bore in the supporting part 1. This action serves to resist swaying of the bottle as it is transported suspended from the gripping device. The achievement of such a secondary force is dependent on a relative movability between the surface of the bevel 8 and the step 9 present on the object being gripped. For such a gripping ring elastomeric materials with a Shore hardness of at 70 Shore A are therefore preferred.

Claims

1. A gripping device for rotationally symmetrical components, consisting of a supporting part with at least one circumferential groove having a connection for a liquid or gaseous working medium, and a movable gripping ring arranged in the groove, of an elastomeric material, with on each end surface at least one sealing lip, which engages slidingly against the respective end wall of the groove.

2. A gripping device according to claim 1, in which the groove is in the outer periphery of a supporting part of peg-like shape.

3. A gripping device according to claim 1, in which the groove is in the inner periphery of the bore of a supporting part of sleeve-like shape. 95

4. A gripping device according to any of claims 1 to 3, in which there is a plurality of grooves and gripping rings, and the connection for the working medium connects together all the grooves.

5. A gripping device according to any of claims 1 to 4, in which the cross section of the gripping ring is similar to the cross section of the groove, and the sealing lips are arranged as projecting annular beads on the corners between the respective end surfaces and the outer or inner periphery of the gripping ring.

6. A gripping device according to claim 5, in which the axial length of the body of the gripping ring is from 0.8 to 3 times the radial thickness of the body. 110

7. A gripping device according to claim 5 or claim 6, in which at least one of the corners between the end surfaces and the outer or inner periphery is bevelled on the side away from the sealing lips. 115

8. A gripping device according to claim 7, in which the bevel includes an angle of 45 to 800 with the axis of rotaion, and the bevel amounts at a maximum to 50% of the radial extent of the end surface of the body of the ring. 120

9. A gripping device according to claim 1, substantially as described with reference to Figure 1 or Figure 2 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.

c